Vehicle fuel systems include evaporative emission control systems designed to reduce the release of fuel vapors to the atmosphere. For example, vaporized hydrocarbons (HCs) from a fuel tank may be stored in a fuel vapor canister packed with an adsorbent which adsorbs and stores the vapors. At a later time, for example when the engine is in operation in a hybrid vehicle, the evaporative emission control system allows the vapors to be purged into the engine intake manifold for use as fuel.
The fuel vapor canister in the hybrid vehicle may primarily store refueling vapors. Further, vapors from running loss and diurnal temperature cycles may not be transferred into the fuel vapor canister and may be contained within the fuel tank. Accordingly, pressure may build in the fuel tank and a higher pressure may exist within the fuel tank. When a vehicle operator indicates a demand to refuel the hybrid vehicle, the fuel cap may be locked until venting of the fuel tank is allowed to sufficiently reduce tank pressure. As such, the fuel cap may be unlocked only after the tank pressure is below a threshold pressure protecting the vehicle operator from being sprayed with fuel vapor.
Previously disclosed systems include a single fuel tank isolation valve (FTIV) between the fuel tank and the fuel vapor canister. The FTIV may be a solenoid valve that is normally closed but the FTIV may be opened to prepare the fuel tank for refueling. However, a constant voltage supply may be provided to energize the FTIV to open and enable depressurization of the fuel tank. As such, the constant supply of voltage to the FTIV may increase power consumption and lead to a rise in maintenance costs. Accordingly, the FTIV may be replaced with a latchable refueling valve. One example latchable refueling valve is shown by Balsdon et al in U.S. 2015/0102039. Therein, a latching mechanism of the latchable refueling valve comprises an index mechanism attached to an armature that may engage with a latch guide to adjust the valve between an open position and a closed position. The valve further includes first and second springs to achieve the adjusting between valve positions. The latchable refueling valve may reduce power consumption but may cause undesirable noises when adjusting between valve positions. Additionally, the large number of components involved with the mechanism may increase maintenance costs.
The inventors herein have recognized the above issues, and have identified an approach to at least partly address the issues. In one example approach, a latching mechanism for a valve comprises an armature including each of an upper and lower offset rounded cam element formed integrally thereon, a rotation sleeve concentrically surrounding the armature and including a plurality of cam guides, a solenoid actuator, a valve core attached to the armature and configured to transmit electromagnetic force into motion against a spring; wherein movement of the armature toward the spring engages the armature cams with the cam guides to impart rotation between the armature and the rotation sleeve, and movement of the armature away from the spring seats the valve in one of a first or second desired valve position. In this way, by reducing the number of moving components and providing rounded cam elements, noises associating with opening and closing the fuel tank isolation valve may be reduced. Additionally, by reducing the number of components in the latchable refueling valve, maintenance costs may be reduced.
As one example, when the latch indices engage the rotation sleeve, the rounded ends of the cam elements may create less noise when engaging with the planar surfaces of the cam guide by reducing the area of contact between the two components. Additionally, by reducing the number of axially moving components of the mechanism to only the armature, a single spring in combination with the solenoid actuator may control the axial motion, thereby reducing the number of parts in the valve.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.